Field of the Disclosure
The present disclosure relates in general to noninvasive patient monitoring systems, including oximeters and co-oximeters, and their accessories such as sensors or cables. In particular, this disclosure relates to patient monitors capable of monitoring the quality of attached accessories.
Description of the Related Art
Patient monitoring of various physiological parameters of a patient is important to a wide range of medical applications. Oximetry is one of the techniques that has developed to accomplish the monitoring of some of these physiological characteristics. It was developed to study and to measure, among other things, the oxygen status of blood. Pulse oximetry—a noninvasive, widely accepted form of oximetry—relies on a sensor attached externally to a patient to output signals indicative of various physiological parameters, such as a patient's constituents or analytes, including for example a percent value for arterial oxygen saturation, carbon monoxide saturation, methenoglobin saturation, fractional saturations, total hematocrit, billirubins, perfusion quality, or the like
A pulse oximeter sensor generally includes one or more energy emission devices, such as specific wavelength emitting LEDs, and one or more energy detection devices. The sensor is generally attached to a measurement site such as a patient's finger, toe, ear, ankle, or the like. An attachment mechanism positions the emitters and detector proximal to the measurement site such that the emitters project energy into the tissue, blood vessels and capillaries of the measurement site, which in turn attenuate the energy. The detector then detects that attenuated energy. The detector communicates at least one signal indicative of the detected attenuated energy to a signal processing device such as an oximeter, generally through cabling attaching the sensor to the oximeter. The oximeter generally calculates, among other things, one or more physiological parameters of the measurement site. In some oximeter systems, specific-valued resistors in the attached sensor provide the signal processing device specific wavelength (“k”) information for the emitters of the sensor. For example, oximeters that capture k information are disclosed in U.S. Pat. No. 4,621,643, entitled “Calibrated Optical Oximeter Probe” and awarded to New, Jr. et al. on Nov. 11, 1986, and U.S. Pat. No. 4,700,708, entitled “Calibrated Optical Oximeter Probe” and awarded to New, Jr. et al. on Oct. 20, 1987.
Patient monitors, generally, and oximeter systems specifically are often highly sensitive instruments. This is especially the case in oximeter systems capable of determining physiological parameters during patient motion, such as those commercially available from Masimo Corporation of Irvine, Calif., and disclosed generally in U.S. Pat. No. 6,263,222, entitled “Signal Processing Apparatus,” and U.S. Pat. No. 6,157,850, also entitled “Signal Processing Apparatus,” U.S. application Ser. No. 09/491,175, entitled “Universal/Upgrading Pulse Oximeter,” and the like, each of which is incorporated herein by reference. The manufacturers of such oximeter systems incorporate into their signal processing algorithms an expectation of a certain type and quality of electronic components in the cabling and sensors. Often the results produced by the signal processing, such as, for example, the output values of various monitored physiological parameters of the patient, are at least somewhat dependent upon receipt of signals from quality electronic components. Thus, many manufacturers carefully control and manage the type and quality of their sensors and accessories.
However, when other sensor manufacturers lure caregivers into purchasing “compatible” sensors, the oximeter manufacturer loses the ability to control the type and quality of the electronic components, the accuracy of their attachment/placement mechanisms, and the like. This is especially problematic with knock-off accessories that attempt to standardize sensor components across differing manufacturers' oximeter systems. For this reason, oximeter manufactures began using the foregoing resistors also as quality control security devices. For example, some oximeter systems look for specific-valued resistors within the circuitry of their sensors, such as, for example, those resistors disclosed in patents entitled “Manual and Automatic Probe Calibration:” U.S. Pat. No. 5,758,644, awarded to Diab et al. on Jun. 2, 1998; U.S. Pat. No. 6,011,986, awarded to Diab et al. on Jan. 4, 2000; and U.S. Pat. No. 6,397,091, awarded to Diab et al. on May 28, 2002. Although such resistor mechanisms improved manufacturer's quality control, some knock off sensor manufactures unfortunately began copying or otherwise scavenging quality control devices from, for example, expired or authorized sensors, thus defeating the quality control device of the original oximeter manufacturer.
Additionally upgrades to patient monitor algorithms and specifications may be made with the expectation that accessories with different optics, higher fidelity, different specifications or the like will be used. A quality check in such an instance can help to ensure that any upgraded algorithms produce more accurate results.